Check an increase rather than current value in check-smart-status.rb

[maoe]

It would be nice if we could check an increase in SMART counters rather than just checking the current values. Could we?

A motivating example is Ultra DMA CRC Error Count. This counter wouldn't be reset even if the problem went away by e.g. replacing the cable. I know I could set an offset using --threshold option but it doesn't scale if there were a tons of servers to be monitored.

[majormoses]

I think we have 2 options:

• check, sleep, check, calculate difference
• check, store results locally to be used on the next check, calculate difference

I think they both have their advantages, with the sleep method it does not require any persistence and would work the first time as expected. With the persistence method the first time it ran would not really work though is probably a non issue with a low interval and more than 1 occurrence.